I have an Accurate Instrument model 257 tube tester. It was working fine for a long time. I placed it on the floor and when I later picked it up the meter movement became defective. The needle rested 1/4 way upscale without any power. It also vibrated and took positions at different points upscale. When I tested a tube the needle deflected and showed the emission of the tube but got stuck at a point again upscale. The zero adjust can only move it a slight amount. Do I need a new meter movement and where can I get one?
Philip

You don't need a new meter (most likely). Remove the front cover from the meter (after removing the meter from the tester). Examine the hair springs carefully. They should not be bent or distorted. The most likely cause for faulty meter movement is from the bearings being loose. To tighten the bearings, loosen the lock nut on the upper bearing. Gently turn in the screw (clockwise) until meter movement is sluggish. Turn out until meter movement just operates freely. Turn just a slight amount more for safety's sake. The movement should not wobble all over the place, though. This is what causes sticking.

ABSOLUTELY NEVER SHOULD YOU BRING ANY DIRT OR METAL FILINGS NEAR THE METER WHILE IT IS OPEN. I cannot stress this enough. This is a rule from God! If you bring any dirt or metal filings, especially metal filings, they'll get into the meter and ruin performance. Metal filings (steel and iron) will not be easily removed from the magnet.

Be extremely careful with the hair springs. If you bend them, meter calibration will be thrown off, and the meter may possibly operate irratically. Though the meter should be lubricated at the bearings, I cannot recommend that you do this unless you have a watch repairman's skill. If you get an excessive amount of oil on the bearings, it will drip down onto the hair springs, which will cause them to stick together, causing irratic meter operation. The only oil to use is the lightest. Trumpet valve oil fits this category. WD-40 does as well, but is not long lived. Still, it lasts for a year or so, and considering that your meter hasn't been lubricated in years, this is probably a good thing. 3-in-1 oil is okay, but a bit too thick. It'll work, but it may run onto the hair springs. Apply by soaking the tip of a tooth pick. Apply a film of oil, not a drop. Rub it onto the shaft point at each bearing. If you use too thick an oil, meter may not respond properly. Normally, however, it'll respond alright, but it may be slowed down.

Thomas

The Accurate 257 uses a inexpensive meter and the magnets have a tendency to flake and collect on the armature causing it to stick. Use thin strips of masking tape and try to pick these particles from between the magnet and armature. Be careful not to disturb the hair springs. The armature pivot should never need adjusting unless the unit has been dropped from an extreme height. Pivot bearings should be dry, if you want to lube them be prepared for trouble in the future. WD-40 is not recommended for this area, at least I won't use it on any meter I repair.

Dave

:I have an Accurate Instrument model 257 tube tester. It was working fine for a long time. I placed it on the floor and when I later picked it up the meter movement became defective. The needle rested 1/4 way upscale without any power. It also vibrated and took positions at different points upscale. When I tested a tube the needle deflected and showed the emission of the tube but got stuck at a point again upscale. The zero adjust can only move it a slight amount. Do I need a new meter movement and where can I get one?
:Philip

::I have an Accurate Instrument model 257 tube tester. It was working fine for a long time. I placed it on the floor and when I later picked it up the meter movement became defective. The needle rested 1/4 way upscale without any power. It also vibrated and took positions at different points upscale. When I tested a tube the needle deflected and showed the emission of the tube but got stuck at a point again upscale. The zero adjust can only move it a slight amount. Do I need a new meter movement and where can I get one?
::Philip
I removed the four screws holding the movement and lifted the movement from the case but how do I remove the plastic cover thereby exposing the movement? It doesn't have any screws. Do I pry it off with a screwdriver?
Philip

Does the meter have a plastic dial cover? The symptoms you describe could be caused by static electrical charge on the cover. These static charges can be surprisingly tenacious. Remove the dial cover and see if that fixes things.

The vibration and bumping around of a tube tester while carrying is enough to disturb the bearing adjustments. The adjustments themselves are not actually upset, but the fine points on the ends of the shafts get dinged from the bouncing. It is always best to treat meters with care (no matter what the value of the meter), and if your meter starts to wobble in the bearings, you can suspect rough handling (putting it in your car, especially on the floor), placing it on the floor of your house a little too solidly, bumping it, carrying it and having it throb against your legs, etc.

Though there are meters which are lubricated, there are indeed meters which are designed to run dry. As I said before, I recommend that you DO NOT lubricate your meter because of trouble with oil getting onto the hairsprings. I have lubricated meters with much success, and I know of several which are designed to be lubricated, but to be on the safe side, you probably shouldn't lubricate any meters. Also, WD-40 is comparable to the lubricants which they use in fine watches and clocks. My uncle was a top watch repairman and jewler for over 70 years, so I have an in on this information. He has repaired my 1941 Bulova 10AX movement many times, and whenever he repaired it or simply cleaned it, it has always kept perfect time. Unfortunately the slightest amount of moisture (sweating) is enough to leave deposits on the gears which upset the time keeping. Also, accidently dropping it on the floor is enough to throw the balance wheel out of position, so you can see why I have had it repaired many times. I keep the watch on the shelf now for the most part and wear an inexpensive battery watch which keeps far superior time without any maintainence. Also, my uncle has died. Other jewlers I know of with just as much expertise charge prohibitive prices. A superb balance wheel/cleaning/mainspring job I had done recently cost me over $140, the price of a rather expensive battery watch. The watch needs a cleaning again, and I'm not up to paying any more money.

Thomas

:Does the meter have a plastic dial cover? The symptoms you describe could be caused by static electrical charge on the cover. These static charges can be surprisingly tenacious. Remove the dial cover and see if that fixes things.
Doug,
The meter does have a plastic cover. And static electrical charge, I think you're right is a candidate for my touble. When I picked it up to look at it the needle was 1/4 upscale. I rubbed the plastic and the needle went down to almost zero. But In trying to get it to zero by rubbing a little more the needle shot up again. I can't get it to move down. But I rubbed again and it went down to almost zero. Turning the zero adjust screw didn't help. Yes this meter is very sensitive. I have to be careful how I move it around, not bumping it or laying it on the floor which started everything. But wait, I brought it to my test bench to test a tube and the needle shot up again. Just carrying it the needle becomes eratic jumping up and down. So I will attempt to try the various suggestions but how to I get the plastic cover off? Do I pry it off?
Philip

Better meters have screws. Your meter may be glued together or may have a groove that the cover snaps onto.

Hopefully someone on here will have a good suggestion for static. I can say try an anti-static record cleaner (if you can find one). You could also try connecting a spring wire to the meter's metal frame which would contact the plastic face in some inconspicuous place. This may or may not help collect the plastic's static charge and neutralize it with the meter "works," which happen to be electrically connected to the needle.....which would then neutralize the needle as well. If this solution works, I think that this would be a more permanent solution than anti-static record cleaner.

Another solution would be to wipe the plastic rear-side with a film of plastic friendly oil. However, this is a very poor idea, as it may affect visibility and it may collect dust, though dust shouldn't be getting into your meter.

Thomas